LIGHT MINERAL OILS (BENZINE)
washed out with alcohol of the same concentration, this being poured into
the cylinder and the volume made up to 100 c.c. and the whole shaken.
Any riitro-deiivatives formed from benzoles present pass into solution in
the alcohol, while the mineral oil remains undissolved; if the volume of
the latter has been diminished by 5 c.c., it is concluded that the oil contained
This procedure is valid only for light oils composed of paraffin hydrocarbons,
which are not attacked by nitric acid.
2. QUANTITATIVE DETERMINATION. This is effected by Kramer and
Bottcher's method, which is based on the absorption'of aromatic hydro-
carbons by sulphuric acid of D 1-84 at 15°, this being prepared from 80
parts of cone, acid and 20 parts of fuming acid. In a flask holding about
75 c.c., surmounted by a long neck graduated in o-i c.c. for 50 c.c., 25 c.c.
of the oil are shaken for 15 minutes with 25 c.c. of the above sulphuric
acid. After a rest of 30 minutes, concentrated sulphuric acid is poured
> -into the flask until the layer of benzine is entirely in the graduated neck,
the volume of this being read off after the lapse of an hour. The difference
between this volume and the original one represents the aromatic hydro-
7. Oil of Turpentine.—The procedure followed is that indicated for
the detection of mineral oils in oil of turpentine (see Chapter on Turpentine
and its Products: Oil of Turpentine, 9, in Vol. II).
Crude light oils are usually yellowish and often contain a certain quantity
of less volatile oils, but the rectified products should be colourless and should
give negative results with the tests described under 5 (above).
Rectified light oils are subdivided, according to the temperature at which
they distil, into different products, named differently in various countries.
Usually the following products are distinguished :
Temperature of Distillation,
Light petroleum ether (Gasoline I) .....
Heavy petroleum ether (Gasoline II, Light benzine) .
Benzine for pleasure automobiles ~) ...
Benzine for ordinary automobiles > Petrols .
Benzine for heavy automobiles ) ...
Benzine properly so-called (Naphtha C)
Ligroin (Naphtha B) .........
Cleaning oil, Naphtha (Naphtha A) .....
Substitute for oil of turpentine ..;....
The limits indicated for the boiling points of petrols are not always alone
to be taken as a basis for judging of their quality, as this depends essentially
on the respective proportions of the various fractions distilling between such
limits. For instance, some brands of benzine distil mainly below 90°—these
being the best—while with others, more than one-half distils above 90°, these
being the least valuable.
The calorific power of petrol is about 11,000-12,000 cals.Rome, 1912. the difference representing the quantity of asphalt and